A stuffing tube penetration consists of a metal cylinder having internal pipe threads on each end. This cylinder is welded to an enclosure or bulkhead, from either side of which it protrudes for a predetermined length. A stuffing tube assembly is installed on each end of the cylinder as the wire or cable is fed through. The assembly consists of a silicone or neoprene rubber packing grommet, a gland ring, a bevel washer, and a nut which is tightened onto the pipe threads to apply the necessary torque for finalizing the installation. The nut, gland ring, and bevel washer must be installed from the end of the wire, because they are not split and installation could not be performed once the wire is in place. Testing of the stuffing tube seals to ensure their integrity against leakage is required, both where the tube enters the enclosure and exits it.
The enclosure is a compartment or area that must be able to maintain pressure with a minimal leak rate. Current practices for a new enclosure involve an air pressurization of the entire enclosure, with a soap bubble check then being performed on each individual stuffing tube penetration. If a new wire or cable has been added to an existing enclosure, then an air blast test may be utilized. This involves applying a direct blast of air to one side of the penetration, at the stuffing tube joint, and performing a soap bubble check at the stuffing tube joint on the other side of the enclosure. The air blast method is not a reliable method of testing for integrity, however.
Where testing requires pressurization of the entire enclosure, such as for new installations, then it is both costly and manpower intensive because the pressurization of the entire enclosure is required to verify individual stuffing tube integrity with a sufficiently reliable level of confidence. Because of these costs and disadvantages for new installations, and because the air blast test for existing installations is considered to be unreliable, then there is a need for an improved test mechanism for inspection of the integrity of stuffing tube joints. Various methods have been attempted, but the problem of establishing a seal around a wire which is not accessible from the end is not an easy task. Previous methods of using a rubber bladder with various combinations of metal cylinders, glue, and a variety of clamping techniques have proven cumbersome and time consuming.
Those skilled in the art will recognize there is a need for an improved method for testing the integrity of stuffing tubes which avoids the costs and disadvantages of the prior art. The disclosed invention provides a reliable method for application of a continuous, regulated source of air pressure to individual stuffing tubes. The invention is a low-cost device which is easy to install, requires a minimum amount of tools, permits several stuffing tubes to be tested at the same time, and utilizes reusable parts. The disclosed invention provides a method of establishing a pressure boundary around joints which are otherwise not accessible from their ends.